Electron discharge device



I Oct. 14, 1958 T. D. FENTRESS ELECTRON DISCHARGE DEVICE Filed Oct. 21,1954 Ir JV! INVENTOR. THOMAS Q ILE/VTR ATTORNEY United States PatentELECTRON DISCHARGE DEVICE Thomas D. Fentress, Shrewsbury, N. 1.,assignor to Bendix Aviation Corporation, Eatontown, N. J., a corporation of Delaware Application October 21, 1954, Serial No. 463,655

2 Claims. (Cl. SIS-5.22)

The present invention relates to high frequency structure and moreparticularly to electron discharge devices embodying such structure.

In certain applications for electron discharge devices, such for exampleas a klystron, it is required that the device be capable of operatingfrom a cold start with a minimum shift in frequency from the start tothat of operation after a predetermined time.

One factor that aifects frequency in electron discharge devices thatutilize resonant cavities is the spacing between the cavity grids.Heretofore, the structure supporting the grid has been of a materialhaving relative high heat conductance in order to conduct heat away fromthe grid and supporting structure. Such material inherently has a highthermal coefiicient of expansion. Hence, during the warm up period, theheat, created by electron bombardment causes expansion of the supportingstructure which changes the spacing between the grids, thereby changingthe operating frequency of the device.

The present invention provides means for overcoming the aforenotedproblem. A supporting member is provided that is made of a materialhaving a low temperature coefiicient of expansion, such for example asInvar. In order to overcome the disadvantage of the low heatconductivity of the material, the support is provided with a heavycopper plating in order to provide a high thermal conductivity path fromthe grid to the wall of the device.

It is an object of the invention to provide an improved electrondischarge device.

Another object of the invention is to provide a novel high frequencystructure.

Another object of the invention is to provide novel means for preventingfrequency shift with changes in temperature in an electron dischargedevice.

Another object of the invention is to provide a novel stabilizedelectron discharge device.

The above and other objects and features of the invention will appearmore fully hereinafter from a con sideration of the followingdescription taken in conjunction with the accompanying drawing whereinone embodiment of the invention is illustrated by way of example.

In the drawing:

The single figure is a cutaway view of an electron discharge deviceembodying the invention.

Reference is now made to the drawing wherein an electron dischargedevice is indicated generally by the numeral 1, which may, for purposesof illustration, be a klystron of the reflex type. Only that portion ofthe device embodying the invention will be described in 2 detail. Thedevice 1 has an envelope 2 inclosing acavity 3. The cavity 3 has a sidewall 4, top wall 5 and bottom wall 6. The top wall 5 has a grid 7supported by a flexible diaphragm 8. The diaphragm 8 may be connected tosuitable tuning apparatus (not shown) for tuning the device 1 over arange of frequencies. It is understood, however, that the grid 7 may befixed and not tunable over a range of frequencies.

The bottom wall 6 is of a substantially inverted cup shapedconfiguration and carries a grid 9 arranged concentric with the grid 7.The wall 6 comprises a base 10 of a material having a low thermalcoefiicient of expansion, such for example as Invar. The base 10 has aheavily plated skin 11 of a material having high thermal conductivity,such for example as copper.

The cavity 3 may be excited by an electron gun 12 of a suitable type. t

In operation the Wall 6 supporting the grid 9 is heated by electronbeams. Heretofore, this heating would cause the structure to expandthereby changing the spacing between the grids '7 and 9. With the wallof a material having a low thermal coefficient of expansion, as long asthe temperature is held within the thermal limits of the material, therewill be a minimum change in spacing with changes in temperature. Theheavy plated skin 11 provides a path of high thermal conductivity fromthe grid support to the envelope 1, thus reducing the internaltemperature of the structure.

Although only one embodiment of the invention has been illustrated anddescribed, various changes in the form and relative arrangement of theparts may be made to suit requirements.

What is claimed is:

1. An electron discharge device having a resonant cavity, a pair ofgrids forming a gap therein, one of said grids being movable for tuningsaid cavity, a fixed support for the other of said grids, an envelopefor enclosing said cavity said fixed support being of a material havinga low thermal coefficient of expansion and having a covering in goodheat exchange relationship therewith of a material having high thermalconductivity and extending from said fixed grid to said envelope toprovide a thermal path from said support to said envelope.

2. A reflex klystron comprising an envelope inclosing a resonant cavity,a movable grid, a fixed grid, means for mounting said movable grid inone wall of said cavity, means for mounting said fixed grid in anopposite wall of said cavity, said last means being constructed of amaterial having a low thermal coefiicient of expansion and having aheavy plating of copper thereon extending from said fixed grid to saidenvelope to provide a thermal path from said fixed grid to saidenvelope.

References Cited in the file of this patent UNITED STATES PATENTS2,337,214 Tunick Dec. 21, 1943 2,374,810 Fremlin May 1, 1945 2,418,844Le Van Apr. 15, 1947 2,468,141 True Apr. 26, 1949 2,503,266 Harrison etal. Apr. 11, 1950 2,508,141 Broadway et al. May 16, 1950 2,513,371Shepherd July 4, 1950 2,523,031 Laflt'erty Sept. 19, 1950

